(1) Field of the Invention
The present invention relates to a thermoplastic resin composition having a good and permanent antistatic property.
(2) Description of the Related Art
Generally, plastics have a large electric resistance and have problems in that they are readily electrically charged by friction or on peeling and attract dust, thus spoiling the appearance thereof. Accordingly, various problems arise in the fields of molded articles, films, sheets and fibers prepared from plastics.
Ordinarily, the following methods are adopted for imparting an antistatic property to plastics.
(1) A method in which an antistatic agent is kneaded into a plastic material.
(2) A method in which an antistatic agent is coated on the surface of a plastic article.
Furthermore, there can be mentioned a method in which a silicon compound is coated on the surface of a plastic article, and a method in which the surface structure of a plastic article is modified by a plasma treatment, but these methods are expensive.
In the method in which an antistatic agent is kneaded into a plastic material, a surface active agent having a low molecular weight is ordinarily used as the antistatic agent. According to this method, however, it is difficult to impart a permanent antistatic property. Namely, if the antistatic agent present on the surface is removed by water washing, friction or the like, the antistatic property is lost. Moreover, there can be mentioned a method using an antistatic rubber, as proposed in Japanese Unexamined Patent Publication No. 55-36237. However, in this method, the antistatic rubber must be incorporated in a large amount and the inherent physical properties of plastics, such as heat resistance, are degraded, and the surface resistance is still about 10.sup.11 .OMEGA. and is not good.
According to the surface coating method with an antistatic agent, a good antistatic property can be attained such that the surface resistance is about 10.sup.9 .OMEGA.. However, the antistatic property is easily lost by water washing, friction or the like. Furthermore, this method is disadvantageous over the kneading method in that the surface coating step is necessary and the cost is increased.
Recently, there is a demand for an antistatic material having a high reliability, for a delivery container or as packaging material for electronic parts. However, an antistatic agent has not been provided which can impart a good and permanent antistatic property with a small incorporated amount without any particular step as described above and does not degrade the inherent properties of a base polymer, and thus the development of such an antistatic agent is eagerly desired in the art.